The present invention relates to systems, methods and apparatus for transmitting radio frequency remote control signals which are particularly advantageous for use in extending the effective operational range of remote control systems employing transmission of control signals in the form of light energy to a controlled device.
A variety of devices are presently in use which are provided with remote control units utilizing light energy as a means of transmission. Many such devices are in common use in the home. Examples of such devices are television receivers, cable converters, VCR's, video disk players, audio reproduction equipment such as compact disk and magnetic tape reproducing equipment, amplifiers, receivers, etc. Each is provided with a device specific hand-held remote control unit which usually employs infrared light as a transmission medium. Typically, the hand-held remote control unit is provided with a number of push button switches for entering control signals manually, encoding circuitry for producing a coded electrical signal uniquely identifying the manually entered command and an infrared light emitter driven to emit infrared light signals corresponding with the encoded commands.
In such systems, the controlled device is provided with an infrared detector to receive the infrared command signal from the hand-held remote control unit and convert the same to an electrical signal to which the remotely controlled device responds by executing the corresponding command. In the case of a remotely controlled television receiver, for example, the command may effect a channel change, volume adjustment, audio mute, or other action which it is convenient for the viewer to implement remotely.
In order to consolidate the functions of multiple remote control units in a single device, hand-held remote control units (also referred to as multi-device units herein) are known which store remote control command codes for various commercially available remotely controlled apparatus such as televisions, VCR's, cable converters and audio devices. Some multi-device units provide the ability to "learn" the codes used by the remote control units specific to such apparatus. Such multi-device units typically emit infrared light signals coded in accordance with the stored codes specific to the various devices to be controlled, and thus serve to replace multiple device-specific remote control units. In order to "learn" the remote control codes of the device-specific remote control units, the multi-device units are provided with an infrared receiver and a microcomputer which can be programmed to store each code for each device to be controlled when the device-specific control unit is operated to transmit the code to be stored to the infrared receiver.
A remote control unit utilizing light energy signal transmission typically must be pointed in the direction of the remote control receiving window of the controlled device to ensure that the command will be received. Moreover, there may be no intervening objects between the remote control unit and the receiving window which might block the line-of-sight transmission path to the window. Such remote control systems are inherently limited to operation within a single room since the intervening walls of the room block transmission of the line-of-sight remote control signals to devices outside the room. This is especially disadvantageous where it is necessary to exercise control of equipment located remotely from a viewer or listener in a different room. For example, a viewer may wish to control a VCR having an infrared remote control system located in a different room reproducing a television signal which is transmitted wirelessly to a television in the viewer's room. A viewer may find it inconvenient to walk to the room where the VCR is located in order to exercise control of the VCR.
U.S. Pat. No. 4,809,359 shows a system for extending the effective operational range of an infrared remote control system which has a first repeater positioned near a remote control unit to receive infrared commands therefrom. The first repeater generates a corresponding radio signal representative of the received infrared signal from the remote control unit. A second repeater adjacent to the controlled device includes a radio receiver which receives the radio signal from the radio transmitter in the first repeater and transmits a corresponding infrared signal toward the controlled device.
While the system shown in U.S. Pat. No. 4,809,359 thus enables an extension of the operational range of an infrared remote control system to other rooms, it is still necessary for the user to ensure that the infrared signal emitted by the remote control unit can be received by the first repeater. This can be distracting and inconvenient for the viewer or listener.
Moreover, the system of U.S. Pat. No. 4,809,359 is relatively complex since it requires the use of two repeaters in addition to the remote control unit. Since the repeaters are located remotely from one another, each typically requires its own source of electrical power (such as an AC/DC converter which must be plugged into a power socket), which adds further to the complexity and inconvenience of the system.